docs: PR 20208 - conan lock upgrade-config path is conanconfig.yml folder

reference/commands/lock/upgrade_config.rst

@@ -19,18 +19,26 @@ The upgrade can be done over individual requirements passed on the command line:
 
   $ conan lock upgrade-config --requires=config/[*] --update-config-requires=config/*
 
-Note that it is important to specify which packages are to be updated with ``--update-config-requires``, because 
+Note that it is important to specify which packages are to be updated with ``--update-config-requires``, because
 it is possible that the lockfile contains more than one configuration package.
 
 Also note that the upgrade of the lockfile doesn't change yet or install the configuration.
 Until a ``conan config install-pkg`` happens, the active and current configuration will not be updated.
 
-It is also possible use a ``conanconfig.yml`` file as an input to the command:
+It is also possible to use a ``conanconfig.yml`` file as an input to the command, by passing the path to
+its containing folder:
 
 .. code-block:: bash
 
   $ conan lock upgrade-config . --update-config-requires=config/1.0
 
+.. important::
+
+    The ``path`` argument must point to a folder containing a ``conanconfig.yml`` file
+    (typically the folder where ``conan config install-pkg`` is executed), not to a ``conanfile.py``
+    or ``conanfile.txt`` recipe. Use ``--requires`` or ``--tool-requires`` to define recipe references
+    directly on the command line.
+
 
 .. seealso::